Assembly and function of Chlamydomonas flagellar mastigonemes as probed with a monoclonal antibody.

Mastigonemes are hair-like projections on the flagella of various kinds of lower eukaryotes. We obtained a monoclonal antibody (mAb-MAST1) to mastigonemes of Chlamydomonas reinhardtii, and found that it reacts with a single flagellar glycoprotein of about 230 kDa. Interestingly, immunofluorescence microscopy demonstrated that mAb-MAST1 recognizes not only the flagellar mastigonemes but also a ring composed of 10 or more particles located in the anterior end of the cell body close to the flagellar bases. The ring structure may be the pool of the mastigoneme protein. When the flagella are amputated, they regenerate to their original length in 90-120 minutes. We found that mastigonemes appear on the new flagellar surface as early as 15 minutes after deflagellation, and that new mastigonemes are mostly assembled onto the distal region of the flagellar surface. Mastigonemes thus appear to be inserted into the membrane only in the distal region of the flagellum. Alternatively, mastigonemes may be inserted at the base and transported very rapidly to the distal portion where they are trapped. When live cells are treated with mAb-MAST1, mastigonemes disappear from the flagellar surface. In these mAb-MAST1 treated cells, the swimming velocity decreases to 70-80% of the normal value, although the flagellar beat frequency increases to approximately 110% of the control. These findings demonstrate vectorial transport of mastigonemes to their assembly sites, and show that mastigonemes function to increase flagellar propulsive force by increasing the effective surface of the flagellum.